Electronic material filler, high-frequency substrate, and electronic material slurry

ABSTRACT

A production method for an electronic material filler includes: a preparation step of preparing a silica particle material produced by a dry method; and a first surface treatment step of performing surface treatment on the silica particle material with a silane compound having a vinyl group, a phenyl group, a phenylamino group, an alkyl group having four or more carbon atoms, a methacryl group, or an epoxy group, to obtain a first surface treatment-processed particle material. After the silica particle material is produced by the dry method, the silica particle material is not brought into contact with liquid water, and has a particle diameter of 100 nm to 600 nm or a specific surface area of 5 m2/g to 35 m2/g.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is based on Japanese application No. 2018-235932,filed on Dec. 17, 2018, the entire contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to an electronic material filler and aproduction method therefor, a production method for an electronicmaterial resin composition, a high-frequency substrate, and anelectronic material slurry.

BACKGROUND ART

An electronic material filler made of a metal oxide particle materialhas been used as sealing materials for semiconductor devices, substratematerials, and other electronic materials, and a resin compositionobtained by dispersing the electronic material filler in a resinmaterial has been especially known (JP-S58-138740(A), JP-S60-199020(A),etc.).

Meanwhile, JP-S60-199020(A) indicates that, when a resin compositionobtained by dispersing a metal oxide particle material in a resinmaterial is applied to an electronic material, preferable result of apressure cooker test is obtained by setting the amount of physicallyadsorbed water in the metal oxide particle material to be dispersed to50 ppm or less. If silica is heated to a temperature higher than 200°C., surface OH groups (bound water) begin to be removed (see, forexample, Surface Chemistry of Powder Particles and Adhesion Phenomenon,Masatoshi CHIKAZAWA and Takashi TAKEI, Bulletin of the Society of SeaWater Science, Japan, 1987, Vol. 41, No. 4, p. 168-180). Thus, thephysically adsorbed water of silica is measured by heating to 200° C.

SUMMARY OF INVENTION Technical Problem

The present inventors have obtained the finding that electriccharacteristics (for example, dielectric loss tangent: Df) are improvedby reducing the amount of contained water (bound water, etc.) inaddition to the amount of physically adsorbed water in applying a metaloxide particle material to an electronic material filler.

Here, in the invention disclosed in JP-560-199020(A), use of particleshaving a relatively large particle diameter is assumed as defined inclaim 1 that the particle diameter is 20 to 100 μm. In recent years,electronic material fillers have become smaller in particle diameterfrom submicron to nanometer order with the miniaturization ofsemiconductor device structures and circuits. The amount of physicallyadsorbed water increases in proportion to the surface area of a particlematerial. Thus, the smaller the particle diameter is, the larger thesurface area and the amount of physically adsorbed water are. Forexample, in the case of a particle material whose particle diameter isdecreased from submicron to nanometer order, the amount of water whichis equivalent to an “amount of water of 50 ppm or less” as defined inJP-S60-199020 (A) is increased by several tens of times and exceeds 1000ppm. Even if heating is performed for the purpose of reducing the amountof water by targeting said amount of water, the amount of containedwater (bound water, etc.) cannot be expected to be reduced to such anextent that improvement of electric characteristics is achieved, andsufficient electric characteristics are not achieved. In particular,even if the amount of physically adsorbed water is reduced, moisture inthe air is sometimes quickly recombined thereafter.

An object of the present invention is to provide an electronic materialfiller having excellent electric characteristics by reducing the amountof contained water other than physically adsorbed water, a productionmethod therefor, a production method for an electronic material resincomposition, a high-frequency substrate, and an electronic materialslurry.

Solution to Problem

(1) A production method for an electronic material filler according tothe present invention solving the above-described problem includes:

a preparation step of preparing a silica particle material produced by adry method; and

a first surface treatment step of performing surface treatment on thesilica particle material with a silane compound having a vinyl group, aphenyl group, a phenylamino group, an alkyl group having four or morecarbon atoms, a methacryl group, or an epoxy group, to obtain a firstsurface treatment-processed particle material, and

after the silica particle material is produced by the dry method, thesilica particle material is not brought into contact with liquid water,and has a particle diameter of 100 nm to 2000 nm or a specific surfacearea of 2 m²/g to 35 m²/g.

By using the silica particle material produced by the dry method and notbringing the silica particle material into contact with water in asubsequent step, the amount of water contained in the silica particlematerial forming an electronic material filler is reduced, and thuselectric characteristics such as a Df value are improved. In particular,the particle diameter is preferably 600 nm or less, and the specificsurface area is preferably 5 m²/g or greater.

The invention of (1) described above may have at least one of thefollowing features (2) and (3).

(2) The production method includes a second surface treatment step ofperforming surface treatment on the first surface treatment-processedparticle material with organosilazane, to obtain a second surfacetreatment-processed particle material, and an amount of theorganosilazane used in the second surface treatment step is equal to orgreater than an amount of functional groups that remain on a surface ofthe first surface treatment-processed particle material and that arecapable of reacting with the organosilazane, and is an amount that doesnot substantially leave OH groups on the surface.

(3) The preparation step includes a drying step of, after the silicaparticle material is produced by a dry method, heating and drying thesilica such that an amount of water produced when heated at 200° C. is40 ppm or less per 1 m² of surface area. This feature is based on thefinding that the value of a dielectric loss tangent is lower when theamount of water produced when heated at 200° C. is 40 ppm or less.

In the present specification, measurement of an amount of water producedwhen heated at a predetermined temperature (for example, 200° C. or 500°C.) is performed by measuring an amount of water produced when heated tothe predetermined temperature, using the Karl Fischer method. The amountof physically adsorbed water is desorbed and measured by heating at 200°C.

By heating at a temperature higher than 200° C. (for example, at 300°C.), bound water is also removed in addition to physically adsorbedwater. If bound water exists, the amount of physically adsorbed watereasily increases. Thus, by reducing bound water, the amount ofphysically adsorbed water is reduced. Even if the amount of waterexceeds 40 ppm, the value of the dielectric loss tangent is notexcessively high in some cases, and electric characteristics such as thedielectric loss tangent are relatively improved by reducing the amountof water.

(4) A production method for an electronic material filler according tothe present invention solving the above-described problem includes:

a silica particle material production step of producing a silicaparticle material by a dry method; and

a drying step of heating and drying the silica particle material suchthat an amount of water produced when heated at 200° C. is 40 ppm orless per 1 m² of surface area, to obtain a dried silica particlematerial, wherein

after the silica particle material is produced by the dry method, thesilica particle material is not brought into contact with liquid water,and has a particle diameter of 100 nm to 2000 nm or a specific surfacearea of 2 m²/g to 35 m²/g.

The electric characteristics are improved by controlling not onlyphysically adsorbed water that is physically adsorbed on the surface ofthe silica particle material, but also the amount of water containedother than the physically adsorbed water. In particular, the particlediameter is preferably 600 nm or less, and the specific surface area ispreferably 5 m²/g or greater.

The invention of (3) or (4) described above may have the followingfeature (5).

(5) The drying step is a step of performing heating and drying such thatan amount of water produced when heated at 500° C. is 70 ppm or less per1 m² of surface area. More firmly bound water is produced by heating toa temperature that exceeds 200° C. and that is equal to or higher than500° C. Since it becomes clear that even such water has an influence onelectric characteristics, the contained amount of such water isspecified.

(6) A production method for an electronic material resin compositionaccording to the present invention solving the above-described problemincludes:

a step of producing an electronic material filler by the above-describedproduction method for an electronic material filler; and

a mixing/dispersing step of mixing and dispersing the electronicmaterial filler in a resin material without bringing the electronicmaterial filler into contact with liquid water. The resin material to beused preferably has a contained amount of water of 1000 ppm or less.

(7) An electronic material filler according to the present inventionsolving the above-described problem is a silica particle material that

has a particle diameter of 100 nm to 2000 nm or a specific surface areaof 2 m²/g to 35 m²/g, and an amount of water, produced when heated at200° C., of 40 ppm or less per 1 m² of surface area, and

is subjected to surface treatment with a silane compound having a vinylgroup, a phenyl group, a phenylamino group, an alkyl group having fouror more carbon atoms, a methacryl group, or an epoxy group. Inparticular, the particle diameter is preferably 600 nm or less, and thespecific surface area is preferably 5 m²/g or greater.

(8) An electronic material filler according to the present inventionsolving the above-described problem is a silica particle material that

has a particle diameter of 100 nm to 2000 nm or a specific surface areaof 2 m²/g to 35 m²/g,

has an amount of water, produced when heated at 200° C., of 40 ppm orless per 1 m² of surface area, and

has a functional group represented by formula (A): —OSiX¹X²X³ and afunctional group represented by formula (B): —OSiY¹Y²Y³ on a surfacethereof, and does not substantially have an OH group on the surfacethereof. In particular, the particle diameter is preferably 600 nm orless, and the specific surface area is preferably 5 m²/g or greater. Inthe formulas (A) and (B): X¹ represents a vinyl group, a phenyl group, aphenylamino group, an alkyl group having four or more carbon atoms, amethacryl group, or an epoxy group; X² and X³ are each independentlyselected from —OSiR3 and —OSiY⁴Y⁵Y⁶; Y¹ represents R; Y² and Y³ are eachindependently selected from R and —OSiY⁴Y⁵Y⁶; Y⁴ represents R; Y⁵ and Y⁶are each independently selected from R and —OSiR3; Rs are eachindependently selected from alkyl groups having one to three carbonatoms; and any of X², X³, Y², Y³, Y⁵, and Y⁶ may be bonded to any of X²,X³, Y², Y³, Y⁵, and Y⁶ of an adjacent functional group via —O—.

(9) A high-frequency substrate according to the present inventionsolving the above-described problem includes the above-describedelectronic material filler and a resin material in which the electronicmaterial filler is dispersed. Since the above-described electronicmaterial filler has a low Df value, the dielectric loss tangent becomessmall, and the loss of power is suppressed by using the electronicmaterial filler for a substrate that handles high frequencies such as ahigh frequency signal. In particular, the resin material preferably hasa contained amount of water of 1000 ppm or less.

(10) An electronic material slurry according to the present inventionsolving the above-described problem includes the above-describedelectronic material filler and a liquid dispersion medium in which theelectronic material filler is dispersed and which does not substantiallycontain water.

The production method for an electronic material filler according to thepresent invention provides an electronic material filler that hasexcellent electric characteristics such as a Df value by having theabove configuration.

DESCRIPTION OF EMBODIMENTS

The electronic material filler and the production method therefor, theproduction method for the electronic material resin composition, thehigh-frequency substrate, and the electronic material slurry accordingto the present invention are described in detail below based on anembodiment.

(Electronic Material Filler)

An electronic material filler according to the present embodiment may beused as materials such as sealing materials for electronic components,substrate materials, and heat transfer materials. In particular, theelectronic material filler according to the present embodiment ispreferably used for a later-described electronic material resincomposition.

The electronic material filler according to the present embodiment is asilica particle material having a particle diameter of 100 nm to 2000 nmor a specific surface area of 2 m²/g to 35 m²/g. The electronic materialfiller has an amount of water, produced when heated at 200° C., of 40ppm or less per 1 m² of surface area.

As for the particle diameter, 150 nm may be adopted as a lower limit,and 1000 nm, 800 nm, 600 nm, and 500 nm may be adopted as an upperlimit. These upper and lower limits may be used in any combination. Theparticle diameter may be measured by a general method such as a dynamicscattering method.

As for the specific surface area, 3 m²/g, 5 m²/g, and 10 m²/g may beadopted as a lower limit, and 30 m²/g may be adopted as an upper limit.These upper and lower limits may be used in any combination. Ameasurement of the specific surface area is a value measured by the BETmethod using nitrogen.

The particle diameter and the specific surface area are correlated witheach other, and the specific surface area tends to be larger when theparticle diameter is smaller. If the particle diameter (specific surfacearea) is set to the lower limit or greater (the upper limit or less),good fluidity is achieved when the electronic material filler is addedinto a resin. If the particle diameter (specific surface area) is set tothe upper limit or less (the lower limit or greater), good stability isachieved when the electronic material filler is used for a slurrycomposition.

The amount of water produced at 200° C. (hereinafter, referred to as“produced water amount 200° C.”) is measured by the Karl Fischer methodas described above. The produced water amount 200° C. is the amount ofwater produced with a temperature increase from normal temperature (25°C.) to 200° C.

As a value of the produced water amount 200° C., an amount of water(ppm) contained per mass of the electronic material filler iscalculated. For a certain electronic material filler, a value of theproduced water amount 200° C. per 1 m² of surface area is calculated bydividing the value of the produced water amount 200° C. by the specificsurface area (m²/g). The upper limit of the value of the produced wateramount 200° C. per 1 m² of surface area is, for example, 40 ppm.

The value of the produced water amount 200° C. per 1 m² of surface areais preferably as low as possible. If the value of the produced wateramount 200° C. is low, the value of a dielectric loss tangent is low.However, even if the value of the dielectric loss tangent is low, thevalue of the produced water amount 200° C. per 1 m² of surface area doesnot necessarily need to be low. A method for adjusting the producedwater amount 200° C. is described later.

Moreover, the amount of water produced at 500° C. (hereinafter, referredto as “produced water amount 500° C.”) is a value calculated when theheating temperature is changed from 200° C. to 500° C. in the method formeasuring the value of the produced water amount 200° C. The value ofthe produced water amount 500° C. per 1 m² of surface area may also becalculated by the same method as the calculation method for the value ofthe produced water amount 200° C. per 1 m² of surface area, except forthe heating temperature. The upper limit of the value of the producedwater amount 500° C. per 1 m² of surface area is preferably 70 ppm. Theproduced water amount 500° C. per 1 m² of surface area is alsopreferably as low as possible.

The electronic material filler according to the present embodiment hasat least either one of the following features (1) and (2).

(1) The electronic material filler is subjected to surface treatmentwith a silane compound having a vinyl group, a phenyl group, aphenylamino group, an alkyl group having four or more carbon atoms, amethacryl group, or an epoxy group. Particularly, the electronicmaterial filler is preferably subjected to surface treatment with asilane compound having a vinyl group, a phenyl group, or an alkyl grouphaving four or more carbon atoms. The amount of the silane compound usedfor the surface treatment is not particularly limited, but is preferablyan amount that allows all OH groups present on the surface of the silicaparticle material before the surface treatment to be eliminated.Infiltration of water into the silica particle material is inhibited byperforming the surface treatment with the silane compound having one ofthese functional groups.

The surface treatment with the silane compound is performed by bringinga surface treatment agent containing the silane compound (for example, asolution obtained by dissolving the silane compound in a solvent) intocontact with the surface of the silica particle material. The surfacetreatment is performed without using water. Here, the term “withoutusing water” means that the amount of water contained in the surfacetreatment agent containing the silane compound is set to 1000 ppm orless. The details are described later.

(2) The electronic material filler has a functional group represented byformula (A): —OSiX¹X²X³ and a functional group represented by formula(B): —OSiY¹Y²Y³ on the surface thereof, and does not substantially havean OH group on the surface thereof. In the formulas (A) and (B): X¹represents a vinyl group, a phenyl group, a phenylamino group, an alkylgroup having four or more carbon atoms, a methacryl group, or an epoxygroup; X² and X³ are each independently selected from —OSiR3 and—OSiY⁴Y⁵Y⁶; Y¹ represents R; Y² and Y³ are each independently selectedfrom R and —OSiY⁴Y⁵Y⁶; Y⁴ represents R; Y⁵ and Y⁶ are each independentlyselected from R and —OSiR3; Rs are each independently selected fromalkyl groups having one to three carbon atoms; and any of X², X³, Y²,Y³, Y⁵, and Y⁶ may be bonded to any of X², X³, Y², Y³, Y⁵, and Y⁶ of anadjacent functional group via —O—.

The functional groups are functional groups that can be introduced bythe surface treatment in (1) described above, or the like. Since thesefunctional groups exist, infiltration of water into the silica particlematerial is inhibited.

(Production Method for Electronic Material Filler: Part 1)

A production method for an electronic material filler according to thepresent embodiment includes a preparation step, a first surfacetreatment step, and other necessary steps. The production method for anelectronic material filler according to the present embodiment is amethod that is suitably used for production of the above-describedelectronic material filler according to the present embodiment. Theproduced electronic material filler has a particle diameter or aspecific surface area that is equal to that of theabove-described-electronic material filler according to the presentembodiment. If the particle diameter, of a silica particle materialproduced in the preparation step described later is decreased, theparticle diameter of the electronic material filler is decreased, andthe specific surface area of the electronic material filler is increased(if the amount of a silane compound to be reacted in the first surfacetreatment step described later is increased, the particle diameter isincreased and the specific surface area is decreased).

Preparation Step

The preparation step is a step of preparing a silica particle materialby a dry method. The dry method is a method for forming a silicaparticle material without contact with water. Examples of the dry methodinclude a VMC method (Vaporized Metal Combustion Method) in which asilica particle material is prepared by burning powder made of a metalsilicon in an oxidizing atmosphere gas and rapidly cooling the powder,and a melting method in which a silica particle material is obtained byputting powder made of silica into a flame to melt the powder and thenrapidly cooling the melted powder. The VMC method and the melting methodare each considered as a dry production method (the dry method in thepresent specification), since powder is put into a high-temperatureatmosphere such as a flame to burn the powder, or since contact withwater is avoided after the powder is heated and melted. In each of theVMC method and the melting method, the particle size distribution of asilica particle material to be prepared is controlled by adjusting theparticle size distribution or amount of powder to be input. For example,if the particle diameter or amount of powder to be input is smaller, theparticle diameter of a silica particle material to be prepared is alsosmaller.

In each of the VMC method and the melting method, the amount of waterpresent in a space into which powder that is a raw material is to be putis preferably reduced. For example, the powder that is a raw material isdispersed in a certain dispersion medium and transported, and the waterin the dispersion medium is preferably removed. In addition, the watercontained in the oxidizing atmosphere gas in the VMC method or in thehigh-temperature atmosphere in the melting method is preferably removed.For removal of water, general dehumidification methods (condensation andremoval of contained water by reducing the temperature, removal of waterwith a desiccant, etc.) may be employed. In addition, when the amount ofwater originally contained is low, the water may also be removed byperforming operations such as using air that changes depending on theseason and weather.

First Surface Treatment Step

The first surface treatment step is a step of performing surfacetreatment on the silica particle material prepared in the preparationstep, to obtain a first surface treatment-processed particle material.The surface treatment is performed with a silane compound. The silanecompound has a vinyl group, a phenyl group, a phenylamino group, analkyl group having four or more carbon atoms, a methacryl group, or anepoxy group. The amount of the silane compound is not particularlylimited, but may be an amount that allows all OH groups present on thesurface of the silica particle material to be reacted. When the surfacetreatment is performed with the silane compound in an amount that leavesOH groups on the surface, a later-described second surface treatmentstep is preferably adopted to react all the OH groups on the surface.

The surface treatment is performed without contact with liquid water.The term “liquid water” means water in the form of a liquid on thesurface of the silica particle material, and includes a liquidcontaining water as well as water obtained by condensing water vapor onthe surface of the silica particle material. If the amount of watercontained is 5000 ppm or greater (preferably 1000 ppm or greater), theliquid is determined as a liquid containing water.

In performing the surface treatment, the silane compound is directlybrought into contact with the surface of the silica particle material,is brought into contact with the surface of the silica particle materialafter being vaporized, or is brought into contact with the surface ofthe silica particle material in a state of being dissolved in a certainsolvent (not containing water) as a solution. During the surfacetreatment, heating may be performed.

Another Step (Second Surface Treatment Step)

The second surface treatment step is a step of performing surfacetreatment on the first surface treatment-processed particle materialproduced in the first surface treatment step, to obtain a second surfacetreatment-processed particle material. The surface treatment isperformed with an organosilazane. The organosilazane is not particularlylimited, but an example thereof is hexamethyldisilazane. The amount ofthe organosilazane for the surface treatment is preferably an amountthat allows all OH groups present on the surface to be reacted.

Another Step (Heating Step)

The heating step is a step of removing the water contained in theelectronic material filler by heating. Conditions for heating are setsuch that the amount of water after the heating step is the amount ofwater described for the above-described electronic material filleraccording to the present embodiment. In the case of a heating step to beperformed in order to satisfy the value of the produced water amount200° C. per 1 m² of surface area, heating is preferably performed at200° C. or higher. In the case of a heating step to be performed inorder to satisfy the value of the produced water amount 500° C. per 1 m²of surface area, heating is preferably performed at 500° C. or higher.The heating step may be performed at a temperature at which the silicaparticle material is not melted or sintered.

During the production process, heating may be performed at any time.However, in particular, heating is preferably performed at the same timeas preparing the silica particle material in the preparation step. Asthe conditions for heating, a temperature and a time at and for whichparticles do not aggregate by heating may be combined. In particular,heating is performed preferably at 200° C. or higher, more preferably at400° C. or higher, and further preferably at 500° C. The heating time isnot particularly limited, but heating is preferably performed until theamount of water reaches the above-described amount of water.

A specific heating method is a method of heating using an electricfurnace or a gas furnace. Specific examples of the apparatus include arotary kiln, a fluidized bed furnace, and a firing furnace.

(Production Method for Electronic Material Filler: Part 2)

A production method for an electronic material filler according to thepresent embodiment includes a silica particle material production stepand a drying step. The silica particle material production step is astep obtained by omitting a drying step from the preparation step in theabove-described production method for an electronic material filler(Part 1). The drying step is the same as the drying step in theabove-described production method for an electronic material filler(Part 1). The particle diameter or specific surface area of the producedelectronic material filler is the same as that in the above-describedproduction method for an electronic material filler (Part 1).

(Production Method for Electronic Material Resin Composition)

A production method for an electronic material resin compositionaccording to the present embodiment includes a step of producing anelectronic material filler by the above-described production method foran electronic material filler according to the present embodiment (Part1 or Part 2), and a mixing/dispersing step of mixing and dispersing theproduced electronic material filler in a resin material without contactwith liquid water. The mixing ratio of the electronic material fillerand the resin material in the produced electronic material resincomposition is not particularly limited, but the contained amount of theelectronic material filler is preferably as large as possible. Forexample, the electronic material filler may be mixed such thatelectronic material filler:resin material is about 10:90 to 90:10 as amass ratio.

The resin material is not particularly limited, but examples thereofinclude general resins such as epoxy resins, polyesters, and siliconeresins. The resin material has a contained amount of water of preferably1000 ppm or less and more preferably 500 ppm or less.

The electronic material filler is preferably subjected to surfacetreatment. The surface treatment is preferably performed such that theaffinity of the electronic material filler with the resin material to beused is improved.

High-Frequency Substrate

A high-frequency substrate according to the present embodiment may beused as a wiring substrate of an electronic device that handles highfrequencies. The electronic material filler according to the presentembodiment has a low Df value, and thus occurrence of loss is reducedeven when the electronic material filler is put to a use in whichapplication at a high frequency is made.

The high-frequency substrate according to the present embodiment is acured product including the above-described electronic material fillerand a resin material in which the electronic material filler isdispersed. The resin material has a contained amount of water ofpreferably 1000 ppm or less and more preferably 500 ppm or less.

The mixing ratio of the electronic material filler and the resinmaterial in the high-frequency substrate is not particularly limited,but the contained amount of the electronic material filler is preferablyas large as possible. For example, the electronic material filler may bemixed such that electronic material filler:resin material is about 10:90to 90:10 as a mass ratio.

The resin material is not particularly limited, but examples thereofinclude general resin materials such as thermosetting resins (before orafter curing) and thermoplastic resins, for example, epoxy resins,melamine resins, acrylic resins, polycarbonate resins, polyesters,silicone resins, liquid crystal polymers (LCPs), polyimides, cyclicolefin polymers (COPs), and polyphenylene oxides (PPOs). A single resinmaterial may be used, or a plurality of types of resin materials may bemixed (alloyed or the like) and used. The resin material has a containedamount of water of preferably 1000 ppm or less and more preferably 500ppm or less.

The electronic material filler is preferably subjected to surfacetreatment. The surface treatment is preferably performed such that theaffinity of the electronic material filler with the resin material to beused is improved.

Electronic Material Slurry

An electronic material slurry according to the present embodiment may beused for a semiconductor substrate material, etc. The electronicmaterial slurry according to the present embodiment includes theabove-described electronic material filler and a liquid dispersionmedium in which the electronic material filler is dispersed. Thedispersion medium does not substantially contain water, and particularlyhas a contained amount of water of preferably 1000 ppm or less and morepreferably 500 ppm or less.

The mixing ratio of the electronic material filler and the dispersionmedium in the electronic material slurry is not particularly limited,but the contained amount of the electronic material filler is preferablyas large as possible. If the mixed amount of the electronic materialfiller is larger, the viscosity tends to be higher. Thus, the electronicmaterial filler may be mixed until the viscosity reaches a viscositythat is permitted in consideration of handleability. For example, theelectronic material filler may be mixed such that electronic materialfiller:resin material is about 20:80 to 80:20 as a mass ratio.

The dispersion medium is not particularly limited, but examples thereofinclude general resin precursors such as organic solvents, silicone oil,epoxy resin precursors, polyester precursors, and silicone resinprecursors.

The electronic material filler is preferably subjected to surfacetreatment. The surface treatment is preferably performed such that theaffinity of the electronic material filler with the dispersion medium tobe used or a mating member that comes into contact when the electronicmaterial filler is finally used is improved.

EXAMPLES

The electronic material filler according to the present invention isdescribed in detail based on Examples.

(Test 1: Evaluation of Heating Temperature in Heating Step)

A silica particle material was produced by burning powder made of ametal silicon in an oxidizing atmosphere gas (VMC method: a silicaparticle material production step). The produced silica particlematerial had a volume average particle diameter of 0.3 μm and a specificsurface area of 16 m²/g. When “dry method” is described as a method forproducing a silica particle material in Examples, a silica particlematerial was produced by the VMC method.

The produced silica particle material was heated at 300° C., 500° C.,700° C., 800° C., and 900° C. (heating step) to prepare samples fromwhich contained water was removed (all the steps are a preparationstep).

The obtained silica particle materials were measured for produced wateramount 200° C. and produced water amount 500° C. according to theabove-described methods. The unit of each amount of water in each tableof the Examples is ppm. The results are shown in Table 1. Furthermore,the sample of each Test Example was measured for dielectric loss tangentat 1 GHz. The measurement of the dielectric loss tangent was performedaccording to JIS C 2138. Specifically, a relative permittivity and adielectric loss tangent were measured at 1 GHz using a network analyzer(E5071C, manufactured by Keysight Technologies, Inc.) and a cavityresonator perturbation method. The measurement was performed accordingto ASTMD2520 (JIS C2565).

TABLE 1 Test Test Test Test Test Test Example 1 Example 2 Example 3Example 4 Example 5 Example 6 Silica particle Dry Dry Dry Dry Dry Drymaterial production step method method method method method methodTemperature in heating 0 300 500 700 800 900 step (° C.) (a) Producedwater 1113 847 777 590 532 423 amount 200° C. (c) Produced water 18681557 1373 1043 928 685 amount 500° C. First surface Not Not Not Not NotNot treatment performed performed performed performed performedperformed Second surface Not Not Not Not Not Not treatment performedperformed performed performed performed performed Average particle 0.30.3 0.3 0.3 0.3 0.3 diameter (μm) (b) Specific surface 16 16 16 16 16 16area (m²/g) a/b 69.6 52.9 48.6 36.9 33.3 26.4 c/b 116.8 97.3 85.8 65.258.0 42.8 Dielectric loss 0.0061 0.0053 0.0041 0.0029 0.0029 0.0017tangent (1 GHz)

As is obvious from Table 1, the value of the dielectric loss tangent wasfound to decrease when the amount of water produced at each temperaturedecreased. The value of the dielectric loss tangent was found to be alsolower when the amount of water produced per unit area when heated at200° C. H (produced water amount 200° C.: ppm)÷(specific surface area:m²/g):a/b] was 40 ppm or less. In addition, the value of the dielectricloss tangent was found to be also lower when the amount of waterproduced per unit area when heated at 500° C. H (produced water amount500° C.: ppm)÷(specific surface area: m²/g):c/b] was 70 ppm or less.After the heating step, even when the sample of each Test Example wasallowed to stand at normal temperature, increases in produced wateramount 200° C. and produced water amount 500° C. were not observed.

(Test 2: Evaluation of Heating Temperature in Heating Step: Case ofPerforming Surface Treatment)

Surface treatment in two stages was performed with vinylsilane andhexamethyldisilazane (HMDS), respectively, on the samples of TestExamples 2 to 6 (a first surface treatment step and a second surfacetreatment step). The surface treatment with vinylsilane was performed inan amount that was about equivalent to twice the amount of surfacesilanol groups. In order to cause all the remaining OH groups to bereacted, the surface treatment with HMDS was performed in an amount thatwas equal to or larger than the amount of the first surface treatmentagent, to obtain test samples of a second surface treatment-processedparticle material. In tests described below, HMDS was also used asorganosilazane in a second surface treatment step.

The obtained test samples (after treatment) were measured for producedwater amount 200° C. and dielectric loss tangent by the methods inTest 1. The results are shown in Table 2. In Table 2, “produced wateramount” at each of (a*) and (c) indicates the amount of water producedwhen the silica particle material before surface treatment was heated ata temperature described thereafter (the same applies hereinafter).

TABLE 2 Test Test Test Test Test Example 7 Example 8 Example 9 Example10 Example 11 Silica particle Dry Dry Dry Dry Dry material productionstep method method method method method Temperature in heating 300° C.500° C. 700° C. 800° C. 900° C. step (° C.) (a*) Produced water 847 777590 532 423 amount 200° C. (c) Produced water 1557 1373 1043 928 685amount 500° C. First surface treatment Vinylsilane VinylsilaneVinylsilane Vinylsilane Vinylsilane Second surface treatment PerformedPerformed Performed Performed Performed Average particle 0.3 0.3 0.3 0.30.3 diameter (μm) (b) Specific surface 16 16 16 16 16 area (m²/g) (a)Produced water amount 541 625 541 508 444 200° C. (after treatment) a*/b52.9 48.6 36.9 33.3 26.4 c/b 97.3 85.8 65.2 58.0 42.8 a/b 33.8 39.1 33.831.8 27.8 Dielectric loss 0.0013 0.0013 0.0013 0.0010 0.0010 tangent (1GHz)

As is obvious from Table 2, the value of the dielectric loss tangent wasfound to be made lower as compared to the test samples of Test Examples2 to 6 before surface treatment, by performing the first surfacetreatment step and the second surface treatment step. The value of thedielectric loss tangent was found to be also lower when the amount ofwater per unit area (a/b) of the particle material after treatment was40 ppm or less.

(Test 3: Evaluation of Silane Compound Used for Surface Treatment andEvaluation of Particle Diameter of Silica Particle Material)

Silica particle materials having a volume average particle diameter of0.5 μm (Test Examples 12 to 16), a silica particle material having avolume average particle diameter of 0.2 μm (Test Example 17), a silicaparticle material having a volume average particle diameter of 0.1 μm(Test Example 18), and a silica particle material having a volumeaverage particle diameter of 2 μm (Test Example 19) were produced bychanging the production conditions of the VMC method in the silicaparticle material production step (preparation step). Each of the silicaparticle materials was heated at 800° C. as a heating step.

Similar to Test Examples 7 to 11, a first surface treatment step and asecond surface treatment step were performed with vinylsilane and HMDSon Test Examples 14 and 17 to 19 to produce second surfacetreatment-processed particle materials as test samples of the respectiveTest Examples. As the first surface treatment step, surface treatmentwas performed with phenylaminosilane, phenylsilane, hexylsilane, anddecylsilane on Test Examples 12, 13, 15, and 16, respectively. In thepost-first surface treatment step, surface treatment was performed in anamount that was about equivalent to twice the amount of surface silanolgroups. The obtained test samples were measured for produced wateramount 200° C. and dielectric loss tangent by the methods in Test 1. Theresults are shown in Table 3.

TABLE 3 Test Test Test Test Example Example Example Example 12 13 14 15Silica particle Dry Dry Dry Dry material production method method methodmethod step Temperature in 800° C. 800° C. 800° C. 800° C. heating step(° C.) (a*) Produced water 148 148 148 148 amount 200° C. (c) Producedwater 244 244 244 244 amount 500° C. First surface Phenylami- Phenyl-Vinyl- Hexyl- treatment nosilane silane silane silane Second surfacePerformed Performed Performed Performed treatment Average particle 0.50.5 0.5 0.5 diameter (μm) (b) Specific surface 5 5 5 5 area (m²/g) (a)Produced water 153 173 166 151 amount 200° C. (after treatment) a*/b29.6 29.6 29.6 29.6 c/b 48.8 48.8 48.8 48.8 a/b 30.6 34.6 33.2 30.2Dielectric loss 0.0009 0.0007 0.0006 0.0007 tangent (1 GHz) Test TestTest Test Example Example Example Example 16 17 18 19 Silica particleDry Dry Dry Dry material production method method method method stepTemperature in 800° C. 800° C. 800° C. 800° C. heating step (° C.) (a*)Produced water 148 489 358 29 amount 200° C. (c) Produced water 244 12191860 377 amount 500° C. First surface Decyl- Vinyl- Vinyl- Vinyl-treatment silane silane silane silane Second surface Performed PerformedPerformed Performed treatment Average particle 0.5 0.2 0.1 2 diameter(μm) (b) Specific surface 5 20 30 2 area (m²/g) (a) Produced water 153463 303 45 amount 200° C. (after treatment) a*/b 29.6 24.5 11.9 14.5 c/b48.8 61.0 62.0 188.5 a/b 30.6 23.2 10.1 22.5 Dielectric loss 0.00070.0013 0.0014 0.0004 tangent (1 GHz)

As is obvious from Table 3, Test Example 14 in which surface treatmentwas performed with vinylsilane as the first surface treatment step wasfound to exhibit a lower value of the dielectric loss tangent ascompared to Test Examples 12, 13, 15, and 16 in which surface treatmentwas performed with phenylaminosilane, phenylsilane, hexylsilane, anddecylsilane, respectively. In addition, the value of the dielectric losstangent was found to also increase when the specific surface area wasincreased as the volume average particle diameter was decreased as inthe order of Test Example 19 (2 μm), Test Example 14 (0.5 μm), TestExample 10 (0.3 μm), Test Example 17 (0.2 μm), and Test Example 18 (0.1μm). Moreover, the value of the dielectric loss tangent was found to bealso lower when the amount of water per unit area (a/b) was 40 ppm orless.

(Test 4: Evaluation of Surface Treatment when Heating Step was notPerformed)

For the samples of Test Examples 18, 17, 7, 14, and 19, surfacetreatment in two stages was performed with vinylsilane andhexamethyldisilazane (HMDS), respectively, on the silica particlematerials before a heating step was performed (a first surface treatmentstep and a second surface treatment step). The surface treatment withvinylsilane was performed in an amount that was about equivalent totwice the amount of surface silanol groups. In order to cause all theremaining OH groups to be reacted, the surface treatment with HMDS wasperformed in an amount that was about equal to or larger than the amountof the first surface treatment agent, to obtain test samples of a secondsurface treatment-processed particle material.

The obtained test samples were measured for produced water amount 200°C. and dielectric loss tangent by the methods in Test 1. The results areshown in Table 4.

TABLE 4 Test Test Test Test Test Example 20 Example 21 Example 22Example 23 Example 24 Silica particle Dry Dry Dry Dry Dry materialproduction step method method method method method Temperature inheating None None None None None step (° C.) (a*) Produced water 28512753 1063 714 105 amount 200° C. (c) Produced water 3626 3739 1959 1219462 amount 500° C. First surface treatment Vinylsilane VinylsilaneVinylsilane Vinylsilane Vinylsilane Second surface treatment PerformedPerformed Performed Performed Performed Average particle 0.1 0.2 0.3 0.52 diameter (μm) (b) Specific surface 30 20 16 5 2 area (m²/g) (a)Produced water amount 345 625 584 173 56 200° C. (after treatment) a*/b95.0 137.7 66.4 142.8 52.5 c/b 120.9 187.0 122.4 243.8 231.0 a/b 11.531.3 36.5 34.6 28.0 Dielectric loss 0.0015 0.0019 0.0014 0.0008 0.0004tangent (1 GHz)

As is obvious from Table 4, from comparison between Test Example 1 (thesilica particle material immediately after production) and Test Example22 (the silica particle material obtained by performing surfacetreatment on the sample of Test Example 1) having a volume averageparticle diameter of 0.3 μm, the value of the produced water amount 200°C. was found to be lower, and the value of the dielectric loss tangentwas found to be also lower, by performing the first surface treatmentstep and the second surface treatment step. Test Example 22 had a highervalue of the dielectric loss tangent than Test Examples 7 to 11 in whichthe heating step was performed, but had a lower value of the dielectricloss tangent than the sample of Test Example 1 and thus was found to besufficiently excellent as an electronic material filler.

Test Examples 20, 21, 23, and 24 having volume average particlediameters of 0.1 μm, 0.2 μm, 0.5 μm, and 2 μm also have values of thedielectric loss tangent slightly higher or equal to those of TestExamples 18, 17, 14, and 19 in which the heating step was performed, andthus were found to be sufficiently excellent electronic materialfillers. In addition, the value of the dielectric loss tangent was foundto be also lower when the amount of water per unit area (a/b) was 40 ppmor less.

(Test 5: Evaluation of Heating Temperature in Heating Step and Value ofProduced Water Amount 200° C.)

A heating step of heating at 800° C. was performed on the silicaparticle material having a volume average particle diameter of 0.1 μm(Test Example 25), the silica particle material having a volume averageparticle diameter of 0.2 μm (Test Example 26), the silica particlematerial having a volume average particle diameter of 0.3 μm (TestExample 27), and the silica particle material having a volume averageparticle diameter of 0.5 μm (Test Example 28) to obtain test samples ofTest Examples 25 to 28. The value of the produced water amount 200° C.and the value of the dielectric loss tangent of each test sample areshown in Table 5.

TABLE 5 Test Test Test Test Example Example Example Example 25 26 27 28Silica particle Dry Dry Dry Dry material production method method methodmethod step Temperature in heating 800° C. 800° C. 800° C. 800° C. step(° C.) (a) Produced water 358 489 532 148 amount 200° C. (c) Producedwater 1860 1219 928 244 amount 500° C. First surface Not Not Not Nottreatment performed performed performed performed Second surface Not NotNot Not treatment performed performed performed performed Averageparticle 0.1 0.2 0.3 0.5 diameter (μm) (b) Specific surface 30 20 16 5area (m²/g) a/b 11.9 24.5 33.3 29.6 c/b 62.0 61.0 58.0 48.8 Dielectricloss 0.0036 0.0028 0.0029 0.0011 tangent (1 GHz)

As is obvious from Table 5, water was sufficiently removed by adoptingthe heating step at a high temperature of 800° C., so that the value ofthe dielectric loss tangent was decreased. The value of the amount ofwater per unit area (a/b) was 40 ppm or less.

(Test 6: Evaluation of Second Surface Treatment Step)

As a first surface treatment step, surface treatment with vinylsilanewas additionally performed on the test samples of Test Examples 25 to 28evaluated in Test 5, to obtain test samples of Test Examples 29 to 32.The amount of vinylsilane was determined by an amount that wasequivalent to twice the amount of surface silanol groups. The resultsare shown in Table 6.

TABLE 6 Test Test Test Test Example Example Example Example 29 30 31 32Silica particle Dry Dry Dry Dry material production method method methodmethod step Temperature in heating 800° C. 800° C. 800° C. 800° C. step(° C.) (a*) Produced water 358 489 532 148 amount 200° C. (c) Producedwater 1860 1219 928 244 amount 500° C. First surface Vinyl- Vinyl-Vinyl- Vinyl- treatment silane silane silane silane Second surface NotNot Not Not treatment performed performed performed performed Averageparticle 0.1 0.2 0.3 0.5 diameter (μm) (b) Specific surface 30 20 16 5area (m²/g) (a) Produced water 90 372 375 197 amount 200° C. (aftertreatment) a*/b 11.9 24.5 33.3 29.6 c/b 62.0 61.0 58.0 48.8 a/b 3.0 18.623.4 39.4 Dielectric loss 0.0017 0.0015 0.0013 0.0008 tangent (1 GHz)

As is obvious from Tables 5 and 6, the value of a/b was found to be madelower than the value (a*/b) before performing the first surfacetreatment step, by performing the surface treatment with vinylsilanewhen the specific surface area was large (larger than 5 m²/g: TestExamples 29 to 31), and the value of the dielectric loss tangent wasfurther found to be lower. Even for the test sample of Test Example 32in which the specific surface area was small and the value of a/b wasnot lower, the value of the dielectric loss tangent was lower.

(Test 7: Evaluation of Bringing into Contact with Water)

A silica particle material having a volume average particle diameter of0.1 μm (Test Example 33) and a silica particle material having a volumeaverage particle diameter of 0.5 μm (Test Example 34) were produced by awet method (sol-gel method), and surface treatment was then performedwith a surface treatment agent containing vinylsilane and water (a firstsurface treatment step). Thereafter, a second surface treatment step wasperformed with a surface treatment agent containing HMDS and water, toobtain test samples.

Moreover, a silica particle material having a volume average particlediameter of 0.3 μm was prepared by a dry method, and then a firstsurface treatment step (containing water) and a second surface treatmentstep that were the same as those for Test Examples 31 and 32 wereperformed to obtain a test sample of Test Example 35. Furthermore, asilica particle material having a volume average particle diameter of0.3 μm was prepared by a dry method, and then a first surface treatmentstep (not containing water) that was the same as that for Test Example 7and a second surface treatment step that was the same as that for TestExamples 33 and 34 were performed to obtain a test sample of TestExample 36. The results are shown in Table 7.

TABLE 7 Test Test Test Test Example Example Example Example 33 34 35 36Silica particle Wet Wet Dry Dry material production method method methodmethod step Temperature in heating None None 800° C. 800° C. step (° C.)(a*) Produced water — — 532 532 amount 200° C. (c) Produced water — —928 928 amount 500° C. First surface Wet Wet Wet Vinyl- treatmentvinylsilane vinylsilane vinylsilane silane treatment treatment treatmentSecond surface Wet Wet Wet Wet treatment treatment treatment treatmenttreatment Average particle 0.1 0.5 0.3 0.3 diameter (μm) (b) Specificsurface 30 5 16 16 area (m²/g) (a) Produced water 7600 7863 2201 7890amount 200° C. (after treatment) a*/b — — 33.3 33.3 c/b — — 58.0 58.0a/b 253.3 1572.6 137.6 493.1 Dielectric loss 0.0441 0.0980 0.0049 0.0100tangent (1 GHz)

Since Test Examples 33 to 36 were brought into contact with liquid waterat any of the stages, the value of the dielectric loss tangent was foundto be a very high value. In addition, the value of a/b was a value muchhigher than 40 ppm. Furthermore, for Test Examples 33 and 34 in whichthe value of the amount of water per unit area (a*/b) before wet surfacetreatment was performed in either one of the first and second surfacetreatment steps was 40 ppm or less, the amount of water was increased byperforming the wet treatment, and thus the value of the dielectric losstangent was also increased.

1. An electronic material filler that is a silica particle material, thesilica particle material having a particle diameter of 100 nm to 2000 nmor a specific surface area of 2 m²/g to 35 m²/g, and an amount of water,generated when heated at 200° C., of 40 ppm or less per 1 m² of surfacearea, and being subjected to surface treatment with a silane compoundhaving a vinyl group, a phenyl group, a phenylamino group, an alkylgroup having four or more carbon atoms, a methacryl group, or an epoxygroup.
 2. An electronic material filler that is a silica particlematerial, the silica particle material having a particle diameter of 100nm to 2000 nm or a specific surface area of 2 m²/g to 35 m²/g, having anamount of water, generated when heated at 200° C., of 40 ppm or less per1 m² of surface area, and having a functional group represented byformula (A): —OSiX¹X²X³ and a functional group represented by formula(B): —OSiY¹Y²Y³ on a surface thereof, and does not substantially have anOH group on the surface thereof, wherein in the formulas (A) and (B): X¹represents a vinyl group, a phenyl group, a phenylamino group, an alkylgroup having four or more carbon atoms, a methacryl group, or an epoxygroup; X² and X³ are each independently selected from —OSiR₃ and—OSiY⁴Y⁵Y⁶; Y¹ represents R; Y² and Y³ are each independently selectedfrom R and —OSiY⁴Y⁵Y⁶; Y⁴ represents R; Y⁵ and Y⁶ are each independentlyselected from R and —OSiR₃; Rs are each independently selected fromalkyl groups having one to three carbon atoms; and any of X², X³, Y²,Y³, Y⁵, and Y⁶ is optionally bonded to an adjacent functional groupwhich is any of X², X³, Y², Y³, Y⁵, and Y⁶ via —O—.
 3. The electronicmaterial filler according to claim 1, wherein the silica particlematerial has a particle diameter of 600 nm or less and a specificsurface area of 5 m²/g or greater.
 4. The electronic material filleraccording to claim 2, wherein the silica particle material has aparticle diameter of 600 nm or less and a specific surface area of 5m²/g or greater.
 5. A high-frequency substrate comprising: theelectronic material filler according to claim 1; and a resin material inwhich the electronic material filler is dispersed.
 6. A high-frequencysubstrate comprising: the electronic material filler according to claim2; and a resin material in which the electronic material filler isdispersed.
 7. The high-frequency substrate according to claim 5, whereinthe resin material has a water content of 1000 ppm or less.
 8. Thehigh-frequency substrate according to claim 6, wherein the resinmaterial has a water content of 1000 ppm or less.
 9. An electronicmaterial slurry comprising: the electronic material filler according toclaim 1; and a liquid dispersion medium in which the electronic materialfiller is dispersed and which does not substantially contain water. 10.An electronic material slurry comprising: the electronic material filleraccording to claim 2; and a liquid dispersion medium in which theelectronic material filler is dispersed and which does not substantiallycontain water.